This research seeks to elucidate some aspects of the normal mechanisms of speech production and perception. One objective is to provide a description of the acoustic and articulatory correlates of the phonetic features, and to attempt to establish some biological basis for phonetic segments and features, possible grounded in quantal principles of production and perception. In particular, we are studying the acoustic characteristics, the production, and the perception of (1) stop consonants, (2) nasal consonants, (3) vowels, and (4) fundamental-frequency changes associated with laryngeal features. A second objective is to determine strategies for the control of the speech production mechanism as the articulatory structures are maneuvered through sequences of target states. The strategies to be studied include coarticulation, reorganization for achieving relatively invariant articulatory target states through different combinations of positions of individual articlators, and peripheral feedback. This work on speech production physiology also includes the development of a model of the tongue and mandible. A third objective is to examine systematically the various modifications that speech sounds undergo when the sounds are concatenated to form syllables, words, and sentences. This research on the characteristics of sentences includes (1) measurements of various properties of speech sounds in context and organization of the data into a set of rules, and (2) the development of models of sentence poduction and the testing of these models through listener evaluations.